| A medium-power class-D audio amplifier is presented in this paper, it is used to drive devices such as flat panel television sets, flat panel monitor sets, multimedia systems, home sound sets and so on. It is a high-efficiency low-power dissipation amplifier implemented with 0.5μm BCD process, and can be used without any external heat sink. The chip can work in voltage from 10V to 36V asymmetrical or±5V to±18V symmetrical, it has two audio channels and can be connected to stereo or mono mode, the RMS output power is 2×15W in stereo mode. This chip is powerful, it supports four operating modes as sleep, mute, operating and fault. Many protections as follows are also built in: thermal foldback, over temperature, over current, over voltage, under voltage, unbalance voltage and so on. And due to special method it has no pop noise when supply turn-on or turn-off.The principle of class-D amplifier is introduced at first in this paper, then the entire topology and sub-block circuits are designed which are satisfied the functional requirements. Some typical circuits are mainly analyzed: reference voltage and other bias voltage circuits, oscillator, mode control circuit, V-I converter, PWM, driver circuit and protection circuits.Base on analyzing circuit theory and designing circuit topology, every sub-block circuit and the entire circuit are simulated by the Cadence Spectre tool. The results of simulation reach the goal and the theory has been verified, then the layout design and layout verification have been done. The results show that, the chip has low THD, good PSRR, CMRR, channel separation and high power efficiency. Comparing with other similar products, this chip has better sound quality, system stability and more overall protections. |
PDF Full Text Request